This paper proposes a new modeling method for finite element analysis (FEA) to reproduce the delamination behavior of fiber-reinforced polymer (FRP) sheet bonded to the concrete. Three-point flexural tests of thin mortar specimens were conducted to clarify the characteristics of the mortar skin which represents concrete surface layer failed at the delamination. The thin mortar specimens that imitate the material composition of the mortar skin and the thin mortar specimens impregnated with primer were tested. In addition, the tensile strength and tensile fracture energy of each mortar skin were determined by inverse analysis using FEA in terms of the flexural stress-displacement relationship obtained from the tests. The flexural strength of the mortar skin in the concrete surface layer was higher than inner part of the concrete block. The strength was increased more when the primer was applied. Furthermore, the material constitutive law of mortar skin was introduced into the FEA. As a result, analytical results generally reproduced load-slip relationship, crack pattern, strain distribution, and bond stress-slip relationship.

本研究において，せん断補強筋を持たない鉄筋コンクリートはりを対象としたせん断耐力予測AIモデルを開発した．その特徴は，ニューラルネットワークに，中立軸のような力学的解釈に基づく説明変数と引張鉄筋の細目に関わる説明変数を組み込んだ点にある．本モデルは，スレンダービームからディープビームまでの幅広い実験結果に対して，従来のニューラルネットワークモデルや実験式よりも高い精度でせん断耐力を予測できる．また，本モデルは，教師データに全く依存しない新規のデータセットに対しても，その適用範囲に留意することで高い精度でせん断耐力を予測できる．さらに，引張補強材にFRPを用いたはりのせん断耐力を，せん断抵抗機構に基づく解釈を本モデルに反映させることで適切に予測できる．

In this study, single-lap shear tests were conducted using carbon fiber-reinforced polymer (CFRP) sheets. The parameters were the stiffness of the multi-ply CFRP sheets and bond length. Furthermore, the bond length and bond width were made larger than that in the previous experiments, in order to approach the actual reinforcement. Consequently, within the range of these tests, the debonding load increased as the number of CFRP sheet layers and stiffness increased. In addition, the three bond strength models showed good agreement. It was clarified that the actual effective bond length may be longer than the effective bond length measured from the strain gauges, owing to the influence of variations in the width direction.

Aiming at improving bond strengths between FRP sheet and concrete, the FRP sheet bonding method using high elongation elastic resin as a buffer layer was developed. In this study, bonding tests was conducted to clarify the basic bond characteristics of FRP strand sheet-concrete interface with a polyurea resin. As a result of the bonding tests, it was found that the use of the polyurea resin as a buffer layer significantly improved the bond strength and the interfacial fracture energy between FRP sheets and concrete. In addition, bond stress-slip relationships with a polyurea resin were proposed. Finally, numerical analyses of bonding CFRP strand sheets and concrete were conducted so as to verify validity of the proposed bond stress-slip relationships. This paper is an extended version in English from the authors' previous work [Kobayashi, A., Ozaki, M., Sato, Y., Arazoe, M., Tateishi, A. and Komori, A., (2020). “Study on bonding behavior of FRP sheets and concrete bonded with high elongation elastic resin.” Journal of Structural Engineering, JSCE, 66A, 855-867. (in Japanese)].